Sequel is a great bare-bones ORM, but the bare-bones quality of Sequel::Model leave something to be desired. For instance the obj.to_json method just calls the default ruby object inspect method, which prints out the class name and memory space. Not helpful. Also no to_xml() for easy REST incorporation. Almost makes me want to go back to ActiveRecord, but then what's the point in using Merb?
Anywho, it's not that hard to extend the functionality of Sequel::Model, so I have started writing some gems to make development with Merb + Sequel a little easier. Like real to_xml & to_json methods on the model instances and instance collections. More on this as it develops.